http://www.npr.org/2011/09/19/140111200/breaking-bad-vince-gilligan-on-meth-and-morals
The AMC drama Breaking Bad stars Bryan Cranston as Walter White, a high school chemistry teacher who has fallen into some financial trouble. When White learns he has terminal lung cancer, something inside him snaps, and he decides to use his familiarity with lab equipment to provide for his medical expenses as well as his family’s future: He teams up with a former student, played by Aaron Paul, and starts dealing crystal meth.
Breaking Bad was created by Vince Gilligan, who previously worked as a producer and writer on The X-Files. He tells Fresh Air’s Terry Gross that he isn’t quite sure where the idea for his critically acclaimed show came from.
"I suspect it had something to do with the fact that when I came up with the idea for Breaking Bad, I was about to turn 40 years old, and perhaps I was thinking in terms of an impending midlife crisis," he says. "To that end, I think Walter White, in the early seasons, is a man who is suffering from perhaps the world’s worst midlife crisis."
Because Walter’s midlife crisis involves cooking and distributing meth, Gilligan had to learn a lot about chemistry — and the drug trade — to convincingly write the show’s dialogue.